// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/memory/shared_memory.h"

#include <mach/mach_vm.h>

#include "base/files/file_util.h"
#include "base/files/scoped_file.h"
#include "base/logging.h"
#include "base/mac/foundation_util.h"
#include "base/mac/mac_util.h"
#include "base/mac/scoped_mach_vm.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/histogram_macros.h"
#include "base/process/process_metrics.h"
#include "base/profiler/scoped_tracker.h"
#include "base/scoped_generic.h"
#include "base/strings/utf_string_conversions.h"
#include "build/build_config.h"

namespace base {

namespace {

    // Returns whether the operation succeeded.
    // |new_handle| is an output variable, populated on success. The caller takes
    // ownership of the underlying memory object.
    // |handle| is the handle to copy.
    // If |handle| is already mapped, |mapped_addr| is its mapped location.
    // Otherwise, |mapped_addr| should be |nullptr|.
    bool MakeMachSharedMemoryHandleReadOnly(SharedMemoryHandle* new_handle,
        SharedMemoryHandle handle,
        void* mapped_addr)
    {
        if (!handle.IsValid())
            return false;

        size_t size;
        CHECK(handle.GetSize(&size));

        // Map if necessary.
        void* temp_addr = mapped_addr;
        base::mac::ScopedMachVM scoper;
        if (!temp_addr) {
            // Intentionally lower current prot and max prot to |VM_PROT_READ|.
            kern_return_t kr = mach_vm_map(
                mach_task_self(), reinterpret_cast<mach_vm_address_t*>(&temp_addr),
                size, 0, VM_FLAGS_ANYWHERE, handle.GetMemoryObject(), 0, FALSE,
                VM_PROT_READ, VM_PROT_READ, VM_INHERIT_NONE);
            if (kr != KERN_SUCCESS)
                return false;
            scoper.reset(reinterpret_cast<vm_address_t>(temp_addr),
                mach_vm_round_page(size));
        }

        // Make new memory object.
        mach_port_t named_right;
        kern_return_t kr = mach_make_memory_entry_64(
            mach_task_self(), reinterpret_cast<memory_object_size_t*>(&size),
            reinterpret_cast<memory_object_offset_t>(temp_addr), VM_PROT_READ,
            &named_right, MACH_PORT_NULL);
        if (kr != KERN_SUCCESS)
            return false;

        *new_handle = SharedMemoryHandle(named_right, size, base::GetCurrentProcId());
        return true;
    }

} // namespace

SharedMemoryCreateOptions::SharedMemoryCreateOptions()
    : size(0)
    , executable(false)
    , share_read_only(false)
{
}

SharedMemory::SharedMemory()
    : mapped_size_(0)
    , memory_(NULL)
    , read_only_(false)
    , requested_size_(0)
{
}

SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
    : shm_(handle)
    , mapped_size_(0)
    , memory_(NULL)
    , read_only_(read_only)
    , requested_size_(0)
{
}

SharedMemory::~SharedMemory()
{
    Unmap();
    Close();
}

// static
bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle)
{
    return handle.IsValid();
}

// static
SharedMemoryHandle SharedMemory::NULLHandle()
{
    return SharedMemoryHandle();
}

// static
void SharedMemory::CloseHandle(const SharedMemoryHandle& handle)
{
    handle.Close();
}

// static
size_t SharedMemory::GetHandleLimit()
{
    // This should be effectively unlimited on OS X.
    return 10000;
}

// static
SharedMemoryHandle SharedMemory::DuplicateHandle(
    const SharedMemoryHandle& handle)
{
    return handle.Duplicate();
}

bool SharedMemory::CreateAndMapAnonymous(size_t size)
{
    return CreateAnonymous(size) && Map(size);
}

// static
bool SharedMemory::GetSizeFromSharedMemoryHandle(
    const SharedMemoryHandle& handle,
    size_t* size)
{
    return handle.GetSize(size);
}

// Chromium mostly only uses the unique/private shmem as specified by
// "name == L"". The exception is in the StatsTable.
bool SharedMemory::Create(const SharedMemoryCreateOptions& options)
{
    // TODO(erikchen): Remove ScopedTracker below once http://crbug.com/466437
    // is fixed.
    tracked_objects::ScopedTracker tracking_profile1(
        FROM_HERE_WITH_EXPLICIT_FUNCTION(
            "466437 SharedMemory::Create::Start"));
    DCHECK(!shm_.IsValid());
    if (options.size == 0)
        return false;

    if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
        return false;

    shm_ = SharedMemoryHandle(options.size);
    requested_size_ = options.size;
    return shm_.IsValid();
}

bool SharedMemory::MapAt(off_t offset, size_t bytes)
{
    if (!shm_.IsValid())
        return false;
    if (bytes > static_cast<size_t>(std::numeric_limits<int>::max()))
        return false;
    if (memory_)
        return false;

    bool success = shm_.MapAt(offset, bytes, &memory_, read_only_);
    if (success) {
        mapped_size_ = bytes;
        DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) & (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
    } else {
        memory_ = NULL;
    }

    return success;
}

bool SharedMemory::Unmap()
{
    if (memory_ == NULL)
        return false;

    mach_vm_deallocate(mach_task_self(),
        reinterpret_cast<mach_vm_address_t>(memory_),
        mapped_size_);
    memory_ = NULL;
    mapped_size_ = 0;
    return true;
}

SharedMemoryHandle SharedMemory::handle() const
{
    return shm_;
}

void SharedMemory::Close()
{
    shm_.Close();
    shm_ = SharedMemoryHandle();
}

bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
    SharedMemoryHandle* new_handle,
    bool close_self,
    ShareMode share_mode)
{
    DCHECK(shm_.IsValid());

    bool success = false;
    switch (share_mode) {
    case SHARE_CURRENT_MODE:
        *new_handle = shm_.Duplicate();
        success = true;
        break;
    case SHARE_READONLY:
        success = MakeMachSharedMemoryHandleReadOnly(new_handle, shm_, memory_);
        break;
    }

    if (success)
        new_handle->SetOwnershipPassesToIPC(true);

    if (close_self) {
        Unmap();
        Close();
    }

    return success;
}

} // namespace base
